Step Function is defined like that:
{
"StartAt": "Decision_Maker",
"States": {
"Decision_Maker":{
"Type": "Choice",
"Choices": [
{
"Variable": "$.body.MyData",
"StringEquals": "null", //that doesn't work :(
"Next": "Run_Task1"
}],
"Default": "Run_Task2"
},
"Run_Task1": {
"Type": "Task",
"Resource": "url_1",
"Next": "Run_Task2"
},
"Run_Task2": {
"Type": "Task",
"Resource": "url_2",
"End": true
}
}
}
Basically it's a choice between 2 tasks. Input data is like this:
{
"body": {
"prop1": "value1",
"myData": {
"otherProp": "value"
}
}
}
The problem is that sometimes there's no myData in JSON. So input may come like this:
{
"body": {
"prop1": "value1",
"myData": null
}
}
How do I check whether or not myData is null?
As of August 2020, Amazon States Language now has an isNull and isPresent Choice Rule. Using these you can natively check for null or the existence of a key in the state input inside a Choice state.
Example:
{ "Variable": "$.possiblyNullValue", "IsNull": true }